1. Field of the Invention
This invention relates to microwave reflector antennas. More particularly, the invention relates to a reflector antenna with a radome and reflector dish interconnection band clamp which enhances signal pattern and mechanical interconnection characteristics.
2. Description of Related Art
The open end of a reflector antenna is typically enclosed by a radome coupled to the distal end of the reflector dish. The radome provides environmental protection and improves wind load characteristics of the antenna.
Edges and/or channel paths of the reflector dish, radome and/or interconnection hardware may diffract or enable spill-over of signal energy present in these areas, introducing undesirable backlobes into the reflector antenna signal pattern quantified as the front to back ratio (F/B) of the antenna. The F/B is regulated by international standards, and is specified by for example, the FCC in 47 CFR Ch. 1 Part 101.115 in the United States, by ETSI in EN302217-4-1 and EN302217-4-12 in Europe, and by ACMA RALI FX 3 Appendix 11 in Australia.
Prior antenna signal pattern backlobe suppression techniques include adding a backlobe suppression ring to the radome, for example via metalizing of the radome periphery as disclosed in commonly owned U.S. Pat. No. 7,138,958, titled “Reflector Antenna Radome with Backlobe Suppressor Ring and Method of Manufacturing” issued Nov. 21, 2006 to Syed et al, hereby incorporated by reference in its entirety. However, the required metalizing operations may increase manufacturing complexity and/or cost, including elaborate coupling arrangements configured to securely retain the shroud upon the reflector dish without presenting undesired reflection edges, signal leakage paths and/or extending the overall size of the radome. Further, the thin metalized ring layer applied to the periphery of the radome may be fragile, requiring increased care to avoid damage during delivery and/or installation.
Reflectors employing castellated edge geometries to generate constructive interference of the edge diffraction components have also been shown to improve the F/B, for example as disclosed in commonly owned Canada Patent No. CA887303 “Backlobe Reduction in Reflector-Type Antennas” by Holtum et al. Such arrangements increase the overall diameter of the antenna, which may complicate radome attachment, packaging and installation.
The addition of a shroud to a reflector antenna improves the signal pattern generally as a function of the shroud length, but also similarly introduces significant costs as the increasing length of the shroud also increases wind loading of the reflector antenna, requiring a corresponding increase in the antenna and antenna support structure strength. Further, an interconnection between the shroud and a radome may introduce significant F/B degradation.
A conventional band clamp 1 applied to retain a radome 3 upon the reflector dish 7 or shroud may introduce diffraction edges and/or signal leakage paths, for example as shown in FIG. 1. Metal taping, RF gaskets or the like may be applied to reduce F/B degradation resulting from band clamp use. However, these materials and procedures increase manufacturing costs and/or installation complexity and may be of limited long-term reliability.
Competition in the reflector antenna market has focused attention on improving electrical performance and minimization of overall manufacturing, inventory, distribution, installation and maintenance costs. Therefore, it is an object of the invention to provide a reflector antenna that overcomes deficiencies in the prior art.